<template>
  <div class="upload-excel">
    <input
      ref="excel-upload-input"
      class="excel-upload-input"
      type="file"
      accept=".xlsx, .xls"
      @change="handleClick"
    >
    <div class="wrapper">
      <!-- 左侧盒子 -->
      <div class="btn-box">
        <el-button
          :loading="loading"
          style="margin-left: 16px"
          size="mini"
          type="primary"
          @click="handleUpload"
        >
          Browse
        </el-button>
        <span
          style="margin-top: 16px"
        >(推荐
          <a
            download="员工导入模板"
            href="/files/员工导入模板.xlsx"
          >下载模板文件</a>
          ,填写后上传)</span>
        <span style="margin-top: 16px">
          <a href="#">点击查看文件上传要求</a>
        </span>
      </div>
      <!-- 右侧盒子 -->
      <div
        class="drop"
        @drop="handleDrop"
        @dragover="handleDragover"
        @dragenter="handleDragover"
      >
        <i class="el-icon-upload" />
        <span>将文件拖到这里</span>
      </div>
    </div>
  </div>
</template>

<script>
import XLSX from 'xlsx'

export default {
  props: {
    // props也是可以传递方法
    beforeUpload: Function, // eslint-disable-line
    onSuccess: Function // eslint-disable-line
  },
  data() {
    return {
      loading: false,
      excelData: {
        header: null,
        results: null
      }
    }
  },
  methods: {
    generateData({ header, results }) {
      this.excelData.header = header
      this.excelData.results = results
      this.onSuccess && this.onSuccess(this.excelData)
    },
    handleDrop(e) {
      e.stopPropagation()
      e.preventDefault()
      if (this.loading) return
      const files = e.dataTransfer.files
      if (files.length !== 1) {
        this.$message.error('只能传一个哦!')
        return
      }
      const rawFile = files[0] // only use files[0]
      if (!this.isExcel(rawFile)) {
        this.$message.error(
          '只能解析 .xlsx, .xls, .csv 这几个类型的文件哦,别乱传哦!'
        )
        return false
      }
      this.upload(rawFile)
      e.stopPropagation()
      e.preventDefault()
    },
    handleDragover(e) {
      e.stopPropagation()
      e.preventDefault()
      e.dataTransfer.dropEffect = 'copy'
    },
    handleUpload() {
      // 点击拖拽框中的按钮 会帮我们偷偷的点击 选择文件标签
      this.$refs['excel-upload-input'].click()
    },
    handleClick(e) {
      const files = e.target.files
      const rawFile = files[0] // only use files[0]
      if (!rawFile) return
      this.upload(rawFile)
    },
    upload(rawFile) {
      this.$refs['excel-upload-input'].value = null // fix can't select the same excel
      if (!this.beforeUpload) {
        this.readerData(rawFile)
        return
      }
      const before = this.beforeUpload(rawFile)
      if (before) {
        this.readerData(rawFile)
      }
    },
    readerData(rawFile) {
      this.loading = true
      return new Promise((resolve, reject) => {
        const reader = new FileReader()
        reader.onload = (e) => {
          const data = e.target.result
          const workbook = XLSX.read(data, { type: 'array' })
          const firstSheetName = workbook.SheetNames[0]
          const worksheet = workbook.Sheets[firstSheetName]
          const header = this.getHeaderRow(worksheet)
          const results = XLSX.utils.sheet_to_json(worksheet)
          this.generateData({ header, results })
          this.loading = false
          resolve()
        }
        reader.readAsArrayBuffer(rawFile)
      })
    },
    getHeaderRow(sheet) {
      const headers = []
      const range = XLSX.utils.decode_range(sheet['!ref'])
      let C
      const R = range.s.r
      /* start in the first row */
      for (C = range.s.c; C <= range.e.c; ++C) {
        /* walk every column in the range */
        const cell = sheet[XLSX.utils.encode_cell({ c: C, r: R })]
        /* find the cell in the first row */
        let hdr = 'UNKNOWN ' + C // <-- replace with your desired default
        if (cell && cell.t) hdr = XLSX.utils.format_cell(cell)
        headers.push(hdr)
      }
      return headers
    },
    isExcel(file) {
      return /\.(xlsx|xls|csv)$/.test(file.name)
    }
  }
}
</script>

<style lang="scss">
.upload-excel {
  margin-top: 50px;
  margin-bottom: 50px;
  .excel-upload-input {
    display: none;
    z-index: -9999;
  }
  .wrapper {
    display: flex;
    width: 800px;
    margin: 0 auto;
    // 子代
    > div {
      display: flex;
      justify-content: center;
      align-items: center;
      flex-direction: column;
    }
  }
  .btn-box {
    flex: 1;
    border: 2px dashed #bbb;
    // border-right: none;
    margin-right: 60px;
    span {
      font-size: 14px;
      a {
        color: red;
      }
    }
  }
  .drop {
    border: 2px dashed #bbb;
    flex: 1;
    height: 160px;
    // line-height: 160px;
    margin: 0 auto;
    font-size: 24px;
    border-radius: 5px;
    text-align: center;
    color: #bbb;
    position: relative;
    i {
      font-size: 100px;
      color: #bfc4cd;
    }
  }
}
</style>
